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Abstract:

A combustion chamber head of a gas turbine has a base plate 113 provided
with a centric recess 121 in which at least one burner 106 is arranged,
with the base plate 113 being connected to walls of the combustion
chamber 108 and to a burner seal 116 sealing the burner 106 towards the
rim of the recess 121. The burner seal 116 is arranged upstream of the
base plate 113 and can be brought into contact with a collar 118 provided
on the base plate 113 and forming the rim of the centric recess 121. A
holding element 117 of the burner seal 116 is formed as a ring and
arranged upstream of the burner seal 116 and engages with at least one
projection 114 of the base plate 113 in a tension-free state.

Claims:

1. A combustion chamber head of a gas turbine comprising: a base plate
having: a centric recess in which at least one burner can be arranged; at
least one projection; a collar forming a rim of the centric recess; the
base plate being connectable to walls of the combustion chamber and to a
burner seal sealing the at least one burner towards the rim of the
centric recess; the burner seal being arranged upstream of the base plate
to engage the collar; and a holding element arranged upstream of the
burner seal for holding the burner seal, the holding element having an
annular form and engaging the at least one projection in a tension-free
state.

2. The combustion chamber head of claim 1, wherein the holding element
includes at least one locking tab engaging with the projection in a
tension-free state.

3. The combustion chamber head of claim 2, wherein the tab is attached to
an inner rim of the annular holding element.

4. The combustion chamber head of claim 2, wherein the tab is attached to
an outer rim of the annular holding element.

5. The combustion chamber head of claim 4, wherein the projection
includes at least one recess into which the locking tab is inserted.

6. The combustion chamber head of claim 5, wherein the projection
includes at least one recess retainer positioned adjacent the recess
which extends closer toward the base plate than a portion of the locking
tab when the locking tab is positioned in the recess in the tension-free
state to prevent rotation of the locking tab out of the recess.

7. The combustion chamber head of claim 6, wherein the burner seal is
funnel-shaped at an upstream side to facilitate introduction of the
burner.

8. The combustion chamber head of claim 3, wherein the projection
includes at least one recess into which the locking tab is inserted.

9. The combustion chamber head of claim 8, wherein the projection
includes at least one recess retainer positioned adjacent the recess
which extends closer toward the base plate than a portion of the locking
tab when the locking tab is positioned in the recess in the tension-free
state to prevent rotation of the locking tab out of the recess.

10. The combustion chamber head of claim 2, wherein the projection
includes at least one recess into which the locking tab is inserted.

11. The combustion chamber head of claim 10, wherein the projection
includes at least one recess retainer positioned adjacent the recess
which extends closer toward the base plate than a portion of the locking
tab when the locking tab is positioned in the recess in the tension-free
state to prevent rotation of the locking tab out of the recess.

Description:

[0001] This application claims priority to German Patent Application DE 10
2011 014 972.4 filed on Mar. 24, 2011, the entirety of which is
incorporated by reference herein.

[0002] This invention relates to a combustion chamber head of a gas
turbine.

[0003] DE 44 27 222 A1 describes a seal around a gas-turbine burner, which
is arranged downstream of a base plate of the combustion chamber,
projects through a heat shield into the combustion chamber and
compensates for movements between the burner fastened inside the
combustion chamber casing and the combustion chamber itself, such that no
inacceptable leakages result. This type of seal does not need to be
gas-tight in the narrower sense.

[0004] DE 100 48 864 A1 presents a seal around a gas-turbine burner, which
is arranged upstream of a base plate of the combustion chamber, projects
through the base plate and a heat shield into the combustion chamber and
fulfills the same function as described in the above.

[0005] As soon as the burner is inserted, the seal can no longer leave its
intended place, but can only be moved in the axial direction along the
burner. The actual sealing force essential for generating and maintaining
the sealing function is usually provided, in the case of gas-turbine
combustion chambers, not by a spring element but by the pressure
difference between the outside of the combustion chamber and its inside,
said pressure difference acting upon the effective surface of the seal.

[0006] Before the burner is inserted, however, and to ensure that the seal
is close to the sealing surface when the gas turbine is started and is
then really pressed by the resultant pressure difference against the base
plate of the combustion chamber or the heat shield, a device must be
provided which positions the seal close to the sealing surface without
exerting pressure. With the solution known from DE 44 27 222 A1, the
axial positioning is set by a spacer disc located between the base plate
of the combustion chamber and the seal. The radial positioning of the
seal before installation of the burner is assured by the shape of the
recess in the base plate of the combustion chamber. With the solution
known from DE 100 48 864 A1, the positioning of the seal in the radial
and axial directions is enabled by crescent-shaped clamps held by the
bolts of the heat shield.

[0007] Another approach to a solution is shown by U.S. Pat. No. 5,419,115
A and U.S. Pat. No. 5,463,864 A, where the guide and seal of the burner
is fitted after the heat shield from the downstream side of the
combustion chamber head, and then fastened upstream of the head by a
one-part or two-part holding means joined to this burner guide. This is
done in such a way that this device including guidance and holding means
can perform minor sliding movements in the radial and lateral directions
in order to permit insertion of the burner, and the relative movements
during operation between the combustion chamber casing in which the
burner is fastened and the combustion chamber can be compensated. Both
publications present different embodiments of an antirotation lock for
the guidance of the burner and its seal, which in some cases are designed
in one piece with the combustion chamber base plate or are fastened
thereto in fixed or moveable manner. U.S. Pat. No. 5,524,438 A represents
in a further variation this antirotation lock as a sheet-metal ring with
radial tabs which engage in recesses of adjacent annular components.
These radial tabs are not used as elastic elements during assembly.

[0008] The solutions known from the state of the art result in the
following disadvantages:

[0009] The spacer discs used in DE 44 27 222 A1 are adapted to the
dimensions of the recess, which slows down assembly. The holding means
proposed in DE 100 48 864 A1 position two seals such that when the nuts
are placed on the bolts of the heat shields three components have to be
held tight, which also renders assembly difficult. The assembly process
provided for in U.S. Pat. No. 5,419,115 A and U.S. Pat. No. 5,463,864 A
in the confined installation space of the combustion chamber head
represents a hard-to-implement process step with a result which is
difficult to check. Overall, all proposed solutions seem complicated,
expensive and difficult due to the many components to be manufactured and
fitted.

[0010] The present invention, in a broad aspect, provides a combustion
chamber head of the type specified at the beginning above which, while
being simply designed and easily and cost-effectively producible features
a simple embodiment of the burner seal and can be assembled easily and at
low cost.

[0011] It is thus provided in accordance with the invention that the
combustion chamber head has a base plate provided with a centric recess
in which at least one burner is arranged. The base plate is connected at
its radially inner and outer areas to walls of the combustion chamber, in
particular to an inner and an outer wall of an annular combustion chamber
(combustion chamber casing). Furthermore, in accordance with the
invention, a burner seal sealing the burner towards the rim of the recess
is provided. The burner seal is, in accordance with the invention,
arranged upstream of the base plate and can be brought into contact with
a collar provided on the base plate and forming the rim of the centric
recess. This results in sealing of the burner seal against the base
plate. It is further provided in accordance with the invention that a
holding element of the burner seal is designed in the form of a ring and
arranged upstream of the burner seal. The annular holding element engages
with at least one projection of the base plate. This projection can, for
example, be designed in the form of a thickened section.

[0012] In a favorable development of the invention, the annular holding
element is provided with at least one locking tab engaging with the
projection (thickened section) of the base plate. The tab is preferably
arranged on the inner ring of the annular holding element, but it is also
possible in accordance with the invention to provide the tab on the outer
ring of the annular holding element.

[0013] To engage the tab in the projection, the latter preferably has a
recess into which the tab can be inserted, in particular by deformation
of the tab.

[0014] To facilitate assembly of the burner, it is particularly favorable
when the burner seal is designed funnel-shaped at its upstream side.

[0015] In accordance with the invention, the seal is provided upstream of
the combustion chamber base plate, where the latter can be brought into
contact with a base plate collar surrounding the recess for passing
through the seal of the burner, where a holding mechanism of the burner
seal is a simple sheet-metal ring with, for example, three outwardly
projecting tabs which engage in recesses in thickened sections of the
base plate of the combustion chamber. At the same time, the burner seal
has at its upstream end a funnel which facilitates assembly of the burner
and has no further function during operation.

[0016] Three projections of the thickened sections of the base plate act
as a permanent reference during mechanical machining of the combustion
chamber head. The tabs on the annular seal holding means can be fitted to
the inner or outer rim of the seal holding means.

[0017] For assembly, the annular holding element (sheet-metal ring) is
laid over the burner seal such that the tabs next to the recesses come to
rest inside the three recesses of the thickened sections of the base
plate. Then the tabs of the annular holding element are pressed down by
an appropriately shaped tool in the direction of the base plate and the
annular holding element is rotated by a small angular amount. As a
result, the tabs engage in the recesses of the thickened section
(projection) of the base plate such that the annular holding element can
no longer turn back, but the tabs can snap back into their original form
without remaining under tension. An antirotation lock for the burner seal
itself is not necessary, based on general operational experience, and is
therefore also not used by the assembly proposed here

[0018] During manufacture of the combustion chamber and also later on
during repair of damaged combustion chambers, the same reference points
in the form of projections of thickened sections are available for
mechanical machining of the combustion chamber. Between manufacture and
overhaul of the combustion chamber, these projections of thickened
sections perform the function of a seal holding mechanism. During
assembly, the burner seal is centered by a tool. The holding mechanism of
the burner seal is likewise centered and moved by the tool. Hence the
fitter must grip only one tool and not three parts at the same time. This
makes assembly safe and quick and means that no joining processes at all
are necessary. This permits a precise, repeatable, easy and inexpensive
assembly. Thanks to the tension-free state of the holding mechanism in
the engaged state, there are no signs of fatigue during operation of the
engine. During the entire service life of the burner seal, the latter is
held close to the combustion chamber head. The sealing force is generated
by the pressure difference between the air flowing around the combustion
chamber and the air in the combustion chamber, and not by the holding
mechanism of the burner seal. Thanks to the integrated supply funnel,
this function does not require any additional component which would in
turn have to be dependably fastened in a manner safe for operation. The
costs for manufacture and assembly of an antirotation lock are saved,
since this function is not needed.

[0019] The present invention is described in the following in light of the
accompanying drawing, showing preferred embodiments. In the drawing,

[0020] FIG. 1 shows a schematic representation of a gas-turbine engine in
accordance with the present invention,

[0021] FIG. 2 shows an enlarged schematic detailed view of a combustion
chamber in accordance with the present invention with appertaining
gas-turbine elements,

[0022] FIG. 3 shows an enlarged detailed sectional view in schematic
representation of an exemplary embodiment of the inventive solution,

[0024] FIG. 5 shows a simplified partial side view of the front plate with
collar and projection,

[0025] FIG. 6 shows a representation by analogy with FIG. 5 of the burner
seal and its holding mechanism in the assembled state,

[0026] FIG. 7 shows a representation by analogy with FIGS. 5 and 6 of a
further exemplary embodiment with assembled burner seal and holding
mechanism, and

[0027] FIG. 8 shows simplified representations of exemplary embodiments of
the holding mechanism in accordance with the present invention.

[0028] The gas-turbine engine 10 in accordance with FIG. 1 is an example
of a turbomachine where the invention can be used. The following however
makes clear that the invention can also be used in other turbomachines.
The engine 10 is of conventional design and includes in the flow
direction, one behind the other, an air inlet 11, a fan 12 rotating
inside a casing, an intermediate-pressure compressor 13, a high-pressure
compressor 14, combustion chambers 15, a high-pressure turbine 16, an
intermediate-pressure turbine 17 and a low-pressure turbine 18 plus an
exhaust nozzle 19, all of which being arranged about a central engine
axis 1.

[0029] The intermediate-pressure compressor 13 and the high-pressure
compressor 14 each include several stages, of which each has an
arrangement extending in the circumferential direction of fixed and
stationary guide vanes 20, generally referred to as stator vanes and
projecting radially inwards from the engine casing 21 in an annular flow
duct through the compressors 13, 14. The compressors furthermore have an
arrangement of compressor rotor blades 22 which project radially outwards
from a rotatable drum or disc 26 linked to hubs 27 of the high-pressure
turbine 16 or of the intermediate-pressure turbine 17, respectively.

[0030] The turbine sections 16, 17, 18 have similar stages, including an
arrangement of fixed guide vanes 23 projecting radially inwards from the
casing 21 into the annular flow duct through the turbines 16, 17, 18, and
a subsequent arrangement of turbine blades 24 projecting outwards from a
rotatable hub 27. The compressor drum or compressor disc 26 and the
blades 22 arranged thereon, as well as the turbine rotor hub 27 and the
turbine rotor blades 24 arranged thereon rotate about the engine axis 1
during operation.

[0031] FIG. 2 shows in a simplified schematic representation the area of a
combustion chamber 108 of a gas turbine. This includes an inner
combustion chamber casing 109 and an outer combustion chamber casing 110.
Upstream of the combustion chamber 108 is arranged a combustion chamber
head 107 in which several burners 106 with arm and head are arranged. The
air is supplied to the combustion chamber 108 via a front blower 101
(fan) driven by a drive shaft 102. A compressor 103 is also connected to
the drive shaft 102. The reference numeral 104 shows a bypass flow
(bypass duct). The onflowing air is passed via a compressor outlet stator
105 with diffusor. The flow exiting the combustion chamber 108 is passed
through a turbine stator 111 and a turbine rotor 112.

[0032] FIG. 3 shows in a schematic detailed view an exemplary embodiment
of the inventive solution. In accordance with the invention, a base plate
113 provided with a recess which is delimited by a collar 118 is arranged
at the upstream end area of the combustion chamber 108. The burners 106
pass through the recess, as shown in FIGS. 1 and 2. The base plate 113 is
provided with a projection 114 (thickened section). The thickened section
114 mounts a burner seal 116 of annular design inside a recess 115, as is
known from the state of the art. The burner seal 116 is held by a holding
element 117 (holding ring), as described in the following figures. To
facilitate assembly of the burner, the burner seal 116 is funnel-shaped
at its upstream side (to the left in FIG. 3).

[0033] FIG. 4 shows a part of the circularly designed base plate 113
provided with the collar 118 which delimits the recess 121 for passing
through one of the burner 106. Three projections 114 (thickened sections
of the base plate 113) are distributed around the circumference of the
collar 118.

[0034] FIG. 5 shows a schematized partial sectional side view of the base
plate 113 with the collar 118 and a projection 114 with a recess 115.
FIG. 6 shows the arrangement shown in FIG. 5 in the assembled state of
the annular burner seal 116 as well as the holding element 117 (holding
ring). The holding element 117 includes a locking tab (tab) 120, as will
be described below. FIG. 6 shows here the arrangement of the locking tab
120 on the radially outer area of the holding element 117, as shown in
the right-hand half of FIG. 8. Three locking tabs (tabs) 120 are shown
here distributed around the circumference.

[0035] FIG. 7 shows a variant in which the locking tab 120 is inserted
into the recess 115 of the projection 114. Recess retainer 122 provides a
positive stop for the locking tab 120. The locking tab is depressed/bent
toward the base plate 113 to clear the recess retainer 122 as the holding
element 117 is rotated into locking position until the tab 120 clears the
recess retainer 122 and returns to its normal non-depressed state,
positioned further away from the base plate 113 within the recess 115. In
this way, the tab 120 has sprung back to be at a level height with the
recess retainer 122 such that the recess retainer 122 prevents back
rotation of the holding element 117 unless the tab 120 is again
depressed. In an alternative embodiment, the tab 120 can have a flat
normal position and is bent into the retention position aside the recess
retainer 122 after being rotated into the recess 115. Hence the
completely assembled state is shown.

[0036] The left-hand half of FIG. 8 shows the annular/ring form of the
holding element 117. The right-hand half of FIG. 8 shows variants of the
locking tabs, i.e. a locking tab 120a of the seal holding element 117.
The variant of the locking tab 120b is arranged on the outside of the
holding element 117, while the variant of the locking tab 120c is
arranged on the inside of the holding element 117. The locking tabs 120b
and 120c are each shown in the bent state.